The swaybar D bushes are bonded to the bar from factory, so are essentially 'non serviceable' (at least from a factory viewpoint), so as per @rado's example, you can move to a generic D bush and mounting clamp with another clamp on the bar to prevent the bush 'walking'
Personally, while the nivomat suspension was a really neat idea when new, it hasnt aged well and is expensive to replace parts on, a decent more 'current' shock absorber, combined with an appropriate spring will handle better and ride better*
*NB: I never actually got to drive an 850R which Nivomats when brand new.
We do Eibach and H&R offerings for springs. With COVID and whatever the excuse for shipping delays has been, we've experienced delays or 'nil stock' on both at various points in the last two years.
In a nutshell -
Eibach - Slightly lower than H&R. A little firmer.
H&R - Not quite as low as the Eibach. Progressive rate. a little better running over lane markers and small road bumps but takes a little longer to take a 'set' when you really pitch it into a corner.
I had H&R in my previous V70T5 project and I've got Eibach in current V70T5 project. Both were paired with Bilstein B6 in the rear and rebuilt Ohlins struts upfront.
Got your email. I'm playing catchup right now and will respond in the next half hour.